Figure 1: The Ground/Air Task-Oriented Radar will perform air surveillance, provide cues to air defense systems, perform counterfire target acquisition, and provide data to air traffic controllers, performing the functions of five different legacy radars.

Figure 1: The Ground/Air Task-Oriented Radar will perform air surveillance, provide cues to air defense systems, perform counterfire target acquisition, and provide data to air traffic controllers, performing the functions of five different legacy radars.
(Source: Official U.S. Marine Corps Web Site)

AN/TPS-80 “G/ATOR”

By Glenn W. Goodman, Jr.

The Ground / Air Task-Oriented Radar (G/ATOR),
in development by the Marine Corps, is a three-dimensional short-to-medium-range tactical radar designed to detect,
identify, and track low-level cruise missiles, manned aircraft, and unmanned aerial vehicles as well as rockets and mortar
and artillery fire. Thanks to advances in
digital radar technology,
the groundbreaking G/ATOR will be a highly mobile, multi-role radar system
that will perform the functions of five different legacy ground-based radars it is slated to replace,
providing increased range, accuracy, tactical mobility, and reliability.

The radar will perform air surveillance, cue air defense weapons, perform
counter-fire target acquisition
(of enemy artillery and mortar firing locations), and provide data to air traffic controllers. Consolidating
these functions into a single multi-role radar will dramatically reduce Marine Corps logistics, operating, and training costs.

The entire G/ATOR system is transported by only two uparmored vehicles – a six-wheel, 7-ton Medium Tactical Vehicle Replacement (MTVR)
all-terrain truck built by Oshkosh, and a single Humvee. In a G/ATOR’s operational configuration, its large radar antenna array is mounted
on a trailer towed by the MTVR vehicle, and is folded down flat during movement. The antenna array remains on the trailer during all operations,
and is elevated for use hydraulically. The trailer has hydraulically controlled leveling legs. The MTVR truck carries a pallet with a generator
and the Humvee carries the radar system’s Communications- Electronic Group (CEG) on a pallet. Both pallets may be lifted off the vehicles during
radar set-up.

G/ATOR will be fielded over time in increments. Increment I,
scheduled for an initial operational capability (IOC) and a fullrate production decision in 2016,
is the air surveillance and short-range air defense radar, which will replace the
TPS-63,
MPQ-62, and
UPS-3 radars.
Increment I will provide all the basic hardware for future increments,
which will add new capabilities through mission-specific software packages.

Increment II, slated for an IOC in 2017,
will add the enemy artillery and mortar targetlocating capability, replacing the existing
TPQ-46
radar. Increment IV, scheduled for an IOC in 2018,
will add military air traffic control functionality, replacing the Marine Corps’
TPS-73
radar and the
Airport Surveillance Radar portion of the
TPN-31A
Air Traffic Navigation, Integration, and Coordination System. Lee Bond, the G/ATOR program manager within the
Program Executive Office for Land Systems, said that Increment III,
which previously encompassed tactical enhancements to the other increments,
has essentially been deferred until the other three increments are well in hand.

The incremental program will allow the Marine Corps to “neck down” over time to only two radars
– the expeditionary short-to-medium-range G/ATOR and the large, transportable
TPS-59(V)3
long-range air surveillance radar.
G/ATOR Increment I also will serve as a gapfiller radar,
covering areas out of view of the TPS-59(V)3 due to line-of-sight limitations.
The TPS-59(V)3 is optimized to track tactical ballistic missiles out to 400 nautical miles and cruise missiles and aircraft out to 300 nautical miles.

With the exception of the MTVR vehicle, the major G/ATOR system components – the trailer with antenna array, the Humvee with the CEG pallet,
and the generator pallet – will be transportable in external sling loads by Marine Corps heavy-lift helicopters and MV-22 Osprey tilt-rotor aircraft.

The key to achieving G/ATOR’s multi-role capabilities within a highly mobile expeditionary system is
active electronically scanned array (AESA)
radar technology. Unlike mechanically scanned radars with curved-dish antennas, an
active phased-array
radar can steer its agile beams electronically.
G/ATOR’s antenna array is made up of 2,600 highly reliable small
solid-state transmit-receive modules,
each a small radar in itself that can alternate between transmitting and receiving.
AESA radars can operate in multiple modes simultaneously and can track significantly more targets than older systems.

G/ATOR has a planar, or flat-face, phased array antenna that is 12 feet tall and 7 feet wide.
The antenna rotates on the trailer at 30 revolutions per minute to provide 360-degree coverage against airborne threats,
mechanically scanning in azimuth and electronically scanning in elevation.
For some missions, the antenna will be stationary and will scan a sector of the airspace it is facing electronically in two dimensions
– azimuth and elevation.

Bond said the need to keep weight down to allow the radar system to be air lifted with rotary-wing aircraft
“drove us to an air-cooled array instead of a more common but much heavier closed-loop liquid cooling system.”
The array has to be kept at a constant temperature across all of its 2,600 transmit-receive modules for peak performance,
he said, and the air cooling has proven to be very effective.
“Despite the fact that G/ATOR has a larger array and sees literally twice as far as the legacy systems it will replace,”
Bond said, “it’s much lighter, primarily due to the AESA active elements on the array and the air cooling system.”

In March 2009, Northrop Grumman successfully completed the G/ATOR program’s Critical Design Review,
the final hurdle before the company began building the first
Increment I engineering development model (EDM) prototype system.
That EDM is now undergoing contractor integration and testing, Bond said.

Marine Corps Program Executive Officer for Land Systems Bill Taylor noted,
“There’s been strong technical progress on this program this past year, and we’re beginning to see real operating hardware.”

Milestone C approval for low-rate initial production of the G/ATOR Increment
I radar system is scheduled in 2013.
The Marine Corps’ Approved Acquisition Objective is a total of 69 G/ATOR systems
– 17 Increment I radars,
38 Increment IIs, and
14 Increment IVs.

In February 2009, then-Under Secretary of Defense for Acquisition, Technology, and Logistics John Young designated G/ATOR,
also referred to as the Multi-Role Radar System, a Department of Defense Special Interest Program that could potentially meet
the ground-based radar requirements of the other services. As a result, the Office of the Secretary of Defense conducts periodic
reviews of the services’ radar programs to ensure commonality as each program is authorized to proceed to its next acquisition milestone.